This is the approach that I would take:Make two 1/2” or 3/4” plywood plates a little larger (at least 2”) in diameter than the canister filter.Cut a hole in the center of one of them to fit over the port on the top of the DC duct.Stack the plates and drill three evenly spaced holes 120º apart thru both plates for three lengths of 5/16” or 3/8” all thread.Cut three lengths of all thread sufficiently long to span the length of the filter plus the thickness of the top plate and the thickness of the bottom plate plus enough length for nuts and washers.Attach the lower plywood plate with the hole to the top of the DC duct with sheet metal screws. Seal the plate to the duct with weather stripping or caulking.Install the canister filter on top of the lower plywood plate and center over the hole. The filter should have a seal ring around the hole in the bottom. (Tip: Mark around the lower edge of the filter with a felt tip marker or install three stop blocks to enable relocating the filter after removal for cleaning.)Install the upper plywood plate on top of the filter with the three holes for the all thread aligned with the lower plate.Install a piece of all thread in each of the three holes and secure with a nut and washer on each end.
CAUTION:Do not overtighten the nuts Tighten only enough to compress the lower seal. It is possible to crush the filter by overtightening.(Tip: When I built my DC, I installed tee nuts in the lower plate and used fluted knobs with thru holes instead of nuts on the top plate. Makes it easier to remove and install without tools.)All thread should be available at your local hardware or Lowes, or Home Depot.Please let me know if you have any more questions.

I use a ratchet tie-down strap over my Jet cartridge. I’m just using one strap—but a second would probably give is a more uniform seal. It’s longer than needed, and bright orange, but is much simpler and effective than the screws on the jet (that require the seal to be compressed and then tightened).

I’ve put a thein baffle in mine—and too am considering the Wynn for more efficiency. I think the ratchet strap will work well and avoid interference w/ the baffle.

Thing I hated about the turnbuckles was that there wasn’t much for them to grab onto and getting them to catch on what little there is was a real pain.

So after a night’s sleep I came back to it this AM and devised a new plan.

The new solve involves using bolts that insert into the unused frame threaded sockets as well as drilling two additional holes into the pressed shell of the DC.

I happened to have some flat bolts and knobs from a bunch of jig pieces hanging around the shop and they worked perfectly.

The new holes are reinforced with washers, cut washers and a nut on the inside, opposite the knobs.

Only minus in this solution is any interruption of air flow where the turnbuckles are, but seeing as it’s merely a slight tweak to Wynn’s original install instructions, I suspect that this will be minimal.

Here are the photos:

Note: In these photos, I’m yet to attach the plastic bag beneath the Wynn cartridge.

Each case will depend—but it seems my outside ratchet strap idea would work in your scenario. You just need to hold the filter down tight. String a couple up one side, over the top of the filter, and down the opposite side. Presumably the filter is sturdy enough to support the tension of the strap. It looks like it would be. You can make the straps are tight as you need to get a snug, but not too snug, fit. And taking off and on is simple. With the Thein baffle, I find I have no need to take the filter off, however—just tap it and blow it off from the outside.